Vacuum tube and tube circuits



Dec. 13, 1927. 7 1,652,880

A. s. THOMAS VACUUM TUBE AND TUBE CIRCUITS Filed July 25, 1923 Ivzuereior: .filer G. Thomas,

Patented Dec. 13, 1927.

ALBERT a. means, or mmcrmnne, vmemu.

PATENT OFF! VAGU'UM TUBE AND TUBE CIRCUITS.

Application filed July 25, 1928. Serial 1T0. 653,784.

This invention relates to new and improved thermionic tubes and tube circuits for use in radio telephony and telegraphy, wire telephony, andother purposes; and to methods of using the same.

One of the objects of this invention is to produce a tube which uses the electronlc stream as a trigger for the release of a current flow through a resistance wh1ch 1s 1onized or'o'therwise varied by electronlc bom bardment. Another object is to provide a tube and tube circuit in which the capac1ty effects in the filament-plate circuit are ameliorated.

With these and other objects in kind, I have conceived the structures and circuits as illustrated in the exemplifications of the avcompanying drawings, in which:

Fig. 1 is a diagrammatic view showing the tube with itsrelated circuit;

Fig. 2 is a view showing a mod1fied c1rcuit, with a slight modification in the tube;

Fig. 3 sh'owsa simplified form of the tube, with a related circuit;

Fight is a diagram of a method or" connecting the tube and the receiver by means of a bridge.

In the drawing, 1 designates an evacuated vessel containing the several elements. F is the filament, G the grid, E the auxiliary plate, and P the plate. The filament F is fed by a suitable battery A with a rheost-at R for regulating the current delivered to the filament. An antenna circuit is shown with the antenna 8, a series condenser C, inductance L, and the ground 11. The inductance L is shown as electromagnetically coupled to the variably positioned secondary inductance U, which may be tuned by the variable condenser C This constitutes .a usual receiving circuit for feeding the grid G through the grid condenser 15 with a, grid leak 14 to allow some of the electrons to escape from the grid G and thus regulate its free potential, and a battery 0; a shortcircuiting switch'17 is provided to elimi- Date the effect of the grid leak and grid condenser when desired. The other terminal of the inductance L is connected with the filament F in the usual manner, with the interposition of an inductance coil L The-auxiliary plate E comprises a thin trons but not the passage of gas molecules. It is disposed within the evacuated vessel 1, between the grid G and the plate P. It may be spherical or cylindrical to conform to the shape of these elements, and is supported in any appropriate manner. The particular form and support for this auxiliary plate may be varied within wide limits, and I have shown it diagrammatically as beinginterposed in its proper location Within the evacuated tube. It has electrodes M and N at the ends, and is filled with material 23 which varies in resistance according to the impact of the electronic stream upon it. A suitable material for this purpose is a solid such as finely granular sodium, closely packed and with each grain partially or wholly insulated by a thin insulating film or coating of suitable material such as thin enamel; or liquids such as solutions of nickel sulfate or sodium chloride, or gases such as mercury vapor. When solids are used, as shown in Fig. 2 I prefer to omit the enclosing tube 2, and to build up a coherent body of these granules as a very thin self-supporting sheet or a thin. layer of the fine particles mounted on a sheet of insulating material, so as to provide practically a surface conductor; to enable the field from a separate plate P to pass, these bodies may have slots or perforations.

Ordinarily, with a proper potential be tween the terminals M and N,- very little or no current will flow through the element E. When electrons from filament F strike the gaseous molecules, for example, contained in the tube, some of them will be ionized and result in additional carriers of electricity. The effective electrical resistance between electrodes M and N will thus be materially decreased, and a greater current will fiow. A similar action occurs with solids or liquids; a movement of the electrons alone occurring in the case of the solids. The terminals M and N of the auxiliary plate E are brought out through the walls ofthe evacuated vessel in known manner, and are connected so as to place the element E in series with an inductance L which is in electromagnetic relation to the inductance L with the telephone or other receiver T, and a telephone battery B, and possibly with a suitable regulating resistance R.

The plate P is connected to a filament lead with the interposition of a suitable battery B or other source to create an electrostatic field between the filament and the late.

The operation of this tube and t e circuit of Fig. 1 may be stated as follows: When a. wave strikes the antenna '8, currents flow as with the ordinary tube, and the electronic stream between the filament F and the late P, as generated and controlled by the cating of the filament F, the electrostatic action of the battery B and the charge on grid G, is caused to fluctuate in correspondence with the variation in intensity of this wave. The plate P is at a positive potential with regard to the filament and acts solely to create the electrostatic field, which draws the electrons towards the auxiliary plate E. The impact of the electronic stream upon the material of the auxiliary plate causes a variation of resistance in this material in proportion to the electron bombardment, by ionization or otherwise, and thereby effects a change in the intensity of the current fiow from the battery B through the receiver T. This causes the telephone to reproduce the wave as a sound.

I have shown the element E as connected in series with an inductance L, which feeds back or regenerates into the secondary c1rcuit by its coupling with the inductance L".

terminals 30, 31, and causes a change of re-.

sistance in the auxiliary plate E as before. The plate P has been disconnected, and the auxiliary plate E is connected in series with telephone T and the battery B. The wave is detected by the variation in resistance of the auxiliary plate.

Fig. 3 shows a circuit wherein the tube is used with only three elements. The battery B is used to create an electrostatic field between the filament and the auxiliary plate E, which in this case also serves as a plate, and is positive with regard to the filament. The electrons then strike E with great velocity if the potential of B is sufiiciently high. This arrangement has the advantage that the electrostatic field is not obstructed. The

- connection of E with the regenerative coil L and the battery B are otherwise as in Fig. 1. The switch S and the resistance R are or the purpose of grounding E when desire Fig. 4 shows a further modification of the circuits which may be utilized with this tube. In it, the telephone T is connected across a current bridge composed of resistances R and R. A third resistance R connectsthe telephone T with one terminal M of the ele' ment E, while the other terminal of the telephone T and terminal N of the element E are connected directly. At the midpoint of the bridge R, R is connected the battery B, whose other terminal'is connected to the resistance R at the far side from the telephone T. This bridge operates similarly to that used with selenium cells for photo-electric purposes.

In Fig. 1, I have also shown a screen S interposed between the filament F and the grid G; and in "Fig. 2 between the id and the element E. This screen S may fashioned of material suited to the material of which thefilling for element E is made, but

may be omitted in certain cases, such as for example when the material of E is a gas not sensitive to light. NVhen using an element E of, for example, sodium, a substance which gives off electrons under the influence of light, the response to the electronic stream is made-more complete if the screen is made of a material opaque to light but transparent to the electrons, such as very thin asbestos or cloth treated so as to be uninflammable and dyed dark. This screen S might, however, be composed of a substance such as the zinc sulfide used in thespinthariscope, in which case the impact of the electrons causes the screen to glow, and thus acts upon the photo-electrically responsive device E disposed behind it, by causing a change of re sistance.

It should be understood in connection with the above that at least two results may occur when an electron moving at high velocity encounters an obstacle such as the plate elements described above: (1) heat is produced which may vary the resistance by the thermal change of conductivity, (2) a number of electrons may be liberated to move at a low velocity, and by their movement vary the effective resistance of the plate element. The first may be accounted for theoretically as the impact of the electron upon a molecule, and the bringing of the latter into agitation. The second is an inter-electronic collision, and may occur with a serious disturbance of a molecule, or the production of heat: it also far predominates in effectiveness over the former, and is in general the effect u on which depends the operation of the p ate element.

What I claim is:

1. In a thermionic tube, an electron-emitting cathode, means to vary the emitted stream of electrons from said cathode at radio frequencies, a plate element in the path of the varying stream of electrons, said late element being of material adapted to iberate free electrons in its mass in proportion to the va ing impact of said stream so that its con uctivity varies in proportion to the variation of the emitted stream of electrons, and means to include said plate element in a circuit.

2. In a thermionic tube, an electron-emitting cathode, a grid,-a plate, said grid having potentials fluctuating at radio frequeneies impressed thereon, means to create an electrostatic field between said cathode and said plate, an element in the path of the elecproportion to the variation of the emitted stream of electrons, and means to include said plate element in a circuit.

' 3. In a vacuum tube system including an electron discharge tube having a cathode, grid and plate elements, said'grid having potentials fluctuatingat radio frequencies impressed thereon, means to create an electrostatic field between said cathode and said plate elements, an output circuit including said plate element in series therein, said plate being composed of material adapted to have free electrons liberated in its mass in proportion to the fluctuating impact of .the electronic stream from said cathode thereupon so that its conductivity varies in proportion to the variation of the emitted stream of electrons, whereby the series resistance of said output circuit is varied'in the same proportion. I

4. In an electron discharge tube system, an electron-emitting cathode, a grid, a plate, an input circuit connected across the cathode and the grid to impress potentials fluctuating at radio frequency upon said grid with respect to said cathode, a space circuit having a source of electricity therein and connecting said cathode and said plate to create an electrostatic field therebetween, an

element disposed in the path of the electronic stream passing from said cathode to said plate under the action of said. field and located between the said grid and the said plate, said element being composed of material electrically responsive to the fluctuating impact. of the electronic stream and in proportion thereto, and an output circuit including said element in series therein.

5. In an electron discharge tube system, an electron-emitting cathode, meansjto vary the stream of electrons emitted from said cathode at radio frequencies, an element disposed in the path of said emitted stream,,

said element being composed of ionizable material, and a circuit including in series said element and a device to indicate the rate of ionization in said element caused by the fluctuating impact of said stream thereupon.

6. In an electron discharge tube, means for emitting a varying stream of electrons, and an element composed of a material having the high ionization characteristics of sodium inthe path of said stream and electrically connected in series in the output circuit of said tube, the resistance of said material changing in substantial accordance with the rate of impact of the varying stream thereupon.

7. In a thermionic tube, an electron emitting cathode, and an element Whose resistance is changed by the impact of the electronic stream, and a light-opaque screen disposed between said cathode and said element.

In testimony whereof I affix my signature.

ALBERT G. THOMAS. 

